The present invention relates generally to orthodontic devices for treating various malocclusions including protrusion and retrusion of the upper teeth relative to the lower teeth, and misalignments of the teeth relative to one another.
A variety of malocclusions have been corrected with conventionally available orthodontic appliances for achieving realignments of the teeth so that an appropriate alignment is established for the upper teeth, for the lower teeth, and between the upper and lower teeth. Early efforts involved the application of orthodontic appliances to the teeth in conjunction with elastic (rubber) bands to apply appropriate forces to the orthodontic appliance and, as a result, to the teeth, as well as removable head gear for interacting with the teeth, to achieve desired movements. Although these techniques have provided satisfactory results, they were found to be subject to certain disadvantages.
The greatest disadvantage of such orthodontic systems is that satisfactory results can only be obtained if a particular device is properly worn. Elastic bands and head gear are rather easily removed by the patient, at times limiting their overall effectiveness. Head gear has the further disadvantage that since the neck), it is cosmetically undesirable and therefore less likely to be properly worn.
Another disadvantage of such orthodontic systems is that they can produce undesirable side effects resulting from undesirable forces that may come to be applied to the orthodontic appliance in addition to those forces which are desired for an effective treatment to take place. These undesirable forces are most prevalent for elastic bands, at times resulting in tooth extrusion and bite opening. Head gear can also result in tooth extrusion. Elastic bands further have the disadvantage of delivering forces that can decay over time, as the elastic elements stretch and fatigue.
Various devices have been developed in an effort to improve upon the elastic bands and head gear of conventional orthodontic appliances. One such attempt involves the use of spring operated devices, primarily to replace the elastic bands. Such devices are disclosed, for example, in U.S. Pat. Nos. 3,618,214 (Armstrong), 4,795,342 (Jones), 5,022,855 (Jeckel) and 5,074,784 (Sterrett et al).
Generally speaking, such devices employ springs to establish tensions similar to those formerly established by elastic bands. However, in practice, it has been found that such devices tend to produce relatively severe and undesirable side effects leading to unwanted tooth extrusion and bite opening. Moreover, most available spring-operated devices are themselves removable (much like the elastic bands they replace), and are often either not worn, lost or broken. For those spring-operated devices that are removable, a common requirement is for the patient to remove the device to eat or to brush the teeth. For those spring-operating devices that are not removable, it is often extremely difficult to clean around such devices. In either case, such devices tend to be bulky, making it difficult for patients to talk with the appliances in place.
Another orthodontic device that has recently found increased acceptance is the so-called "bite jumping" appliance. Such appliances are disclosed, for example, in U.S. Pat. Nos. 3,798,773 (Northcutt), 4,462,800 (Jones), 4,551,095 (Mason), 4,708,646 (Jasper) and 5,183,388 (Kumar).
All except U.S. Pat. No. 4,708,646 disclose variations of a device generally known as the "Herbst" device, and include a metal cylinder containing a plunger and attachable to and between the orthodontic appliances (braces) fixed to the patient's upper and lower teeth. Such devices are rigidly attached to the associated orthodontic appliances and, as a result, cannot be removed by the patient. However, because of their rigid attachment, it is not uncommon for such devices to become damaged, or to cause damage to the orthodontic appliances to which they are attached. Primarily, this results from the lack of flexibility of such devices, and the relatively large forces that can be produced as the patient's jaws are closed (in the normal course).
U.S. Pat. No. 4,708,646 replaces the more conventional Herbst device with an elastic element comprised of a spring surrounded by a rubber core and having metal end caps for attachment to and between the orthodontic appliances associated with the patient's upper and lower teeth. In use, the disclosed elastic element tends to produce extremely high forces, similar to the Herbst device, and is highly susceptible to breakage. Breakage primarily results from the ability of such a device to swivel about its attachment points, producing significant flexure and permitting the device to at times become caught between the patient's upper and lower teeth (and chewed upon). Separation of the end caps from the connecting spring and cover is quite common as a result.
Also to consider is that such devices are primarily directed toward the treatment of retrusion of the lower jaw. Such appliances are not generally useful in treating malocclusions of the teeth that are not related to underlying skeletal defects (such as misalignment of the jaw). The reason for this is that favorable tooth movement is difficult to achieve in view of the relatively heavy forces that are produced by such devices. Because of this, the use of such devices can be disadvantageous when the patient has upper and lower jaws that are correctly aligned, and only movement of the patient's teeth is required (either relative to one another, or relative movement of the upper teeth and the lower teeth). As a result, such appliances can only be used in limited situations.
Consequently, the need remains to provide a device for developing the forces that are appropriate toward effectively interconnecting orthodontic appliances to achieve the movements that are desired for a particular treatment, and which are less subject to the disadvantages of non-use and breakage.